Opening up the unslung control panel (in firefox)…
(USB Port 1 Public Data)/Music Library/Al Green/Call Me/03 Stand Up.m4a
and it says at the top of the unslung file listing:
Current Location: DISK1/Music Library/Al Green/Call Me

If I telnet into the slug, here is the path to the same song:
share/hdd/data/public/Music Library/Al Gree/Call Me/03 Stand Up.m4a

If I open up the iTunes Music Library.xml:
file://localhost//Mediaslug/disk%201/Music%20Library/Al%20Green/Call%20Me/03%20Stand%20Up.m4a